The present invention relates to a computer system such as a work stations and a server, and more particularly to a file server system for making access to a file stored in a secondary storage device at a high speed and a file access control method thereof in a computer system having a multiprocessor structure.
Formation of a computer into a network has been developed in recent years. Keeping step with this, demand for a file server for administrating a file shared among computers collectively is increasing. This is due to such a reason that a file system can be constructed at a low cost. Namely, it is due to such a fact that, since it becomes possible to share a file among a plurality of computers by using a file server, it becomes no longer required to make a plurality of copies of the same file among a plurality of computers and possess them. A network corresponding file system is normally loaded in a file server, and it becomes possible to make access as if it were a file stored in a client computer itself by also loading a network corresponding file system access program in a computer on a client side connected to the same network. As a result, it becomes possible to make access to a file stored and controlled in the file server from any client computer connected to the network, and sharing of a file among a plurality of client computers is realized.
A network corresponding file system is described in Managing NFS and NIS (Hal Stern, O'Reilly & Associates, Inc. June 1991, p. 113 to p. 159).
However, a problem in point of performance is produced sometimes when a file in a file server is shared by using a network corresponding file system. Namely, when file access is made from a plurality of client computers at the same time, the load is concentrated to the file server, thus generating such a situation that access results cannot be obtained immediately.
Therefore, when the load to the file server becomes excessive and an access throughput of the client computer is lowered, it has been performed so that a plurality units of file servers are connected in parallel in the network so as to distribute the access demand from a plurality of client computers. Respective client computers control information on all file servers installed on the network and issue an access request to a file server where an access objective file is in existence by referring to the control information. With this, when access objective files of respective client computers are stored in separate file servers, it becomes possible to distribute load, thus improving the access throughput.
Although it is not of a client-and-server structure, a system which resembles the system mentioned above in points that one main processor controls the whole of plurality of data files and these data files are arranged distributedly in a plurality of sub-processors is described in JP-A-4-48352.